All vehicles are now equipped with seats having a recliner mechanism that can be selectively actuated for permitting the angular position of the seat back to be varied with respect to the seat cushion.
Generally, seat reclining mechanism includes a lower and upper arm mounted on the seat cushion and seat back respectively, to house a locking cum unlocking means, which is effected by a rotatable cam operated by a splined shaft which passes through the lower and upper arms of the recliner. Spiral springs that are mounted on the shaft, are disposed between the two arms of the recliner to apply radial forces on the cam for rotation during locking and unlocking operations.
U.S. Pat. No. 6,626,495 discloses a seat recliner mechanism having a manual control member on a shaft hinge for actuating a cam which in turn helps in disengagement of the first toothed pawls or inner sector member, with the second toothed seat back arm member to allow pivotal movement of the seat back arm which is connected to the seat back to a reclined position.
In the aforementioned seat reclining device, the actuating mechanism includes a hinge shaft directly connected to the cam. The cam is also hooked with the spiral spring. As a result there are two forces acting on the actuating member i.e., the cam. Sometimes, this may result in uneven forces acting on the cam and hence operational difficulties arise as well as increasing the operating effort. The guide walls that guide the pawls or the inner sectors may wear out due to irregular shape and manufacturing process.
The recliner also becomes safety critical mechanism because in the event of a collision the recliner should be able to withstand the impact forces that act on the seat and thus on the recliner, without any major deformations or breakage. The necessity of twin recliner becomes significant when the seat size is increased such that a single recliner fails to endure the subjected loads. Thereby the concept wherein the two recliners share both static and fatigue loads forms an important background of this invention.
U.S. Pat. No. 6,474,740,issued Nov. 5, 2002 and U.S. Pat. No. 6,609,756,issued Aug. 26, 2003,also specifies a reclining device similar to the above mentioned claiming to have reduced rotational friction and noise respectively.
The constraints that limit the functioning of the twin recliner assembly include failure of recliners to operate simultaneously due to loss in transmission, very high operating forces, teeth breakage because of shock forces, slippage due to undershooting and overshooting, endurance failure, so on and so forth.
In the present trend it is desirable to provide a recliner with the simplest mechanism with high strength, less friction between the components and thus free movement of the components for operational ease.
Thus the objective of this invention has been to enhance the operating characteristics of a twin recliner assembly by fulfilling the load carrying and fatigue life requirements and also by reducing the loss in the actuating mechanism between the master and the slave recliners. Further the objective has been to reduce the operating effort and provide a recliner assembly which is designed so as to eliminate the problems in the individual assembly also. It is therefore desirable to have an improved recliner which is easy to both manufacture and operate and is failsafe.